The present invention relates to the removal of pathogenic substances from blood.
Earlier work includes the treatment of blood to remove pathogenic material by a variety of physical means including, for example, dialysis techniques and the like. Hemodialysis, however is not a sufficiently specific procedure. Also if one removes smaller molecules such as salicylates or barbiturates by hemodialysis, the procedure is slow and incomplete because it depends upon the concentration of the poison in the blood plasma. Larger molecules, such as proteins, cannot be removed by dialysis, but only by plasmapheresis and exchange-transfusion procedures. Such procedures remove more of the blood than is actually required. Thus, in plasmapheresis, there is need for replacement fluid. In exchange transfusion, large amounts of blood are needed, and there remains the problem of dealing with antigens such as hepatitis virus from the transfused blood.
More recently, centrifugation of the circulating blood plasma and perfusion over an immunoabsorbent bed has been utilized, under experimental conditions, for the removal of antibodies by Protein A in cancer patients. This procedure requires a complex apparatus for the separation of plasma by centrifugation, separate passage of plasma over the absorbing bed, and subsequent reconsitution with the cellular elements of blood before returning the blood to the patient. The complexity of the process gives rise to errors, and limits its use to specific centers having equipment and necessary highly-trained technicians to operate the equipment. Also there is an undesirable risk of loss of blood components, of hemolysis, or other untoward reactions, particularly since a relatively high fraction of the patients' total blood volume is outside the body during the procedure.
In hindsight, review of other prior art now known to the inventors, it is noted that there are numerous membrane-moderated separation devices known in the art. For example, U.S. Pat. No. 4,375,414 to Strahilevitz discloses immobilizing immunoactive materials on the side of a membrane on which the fluid being treated is flowing or having the material carried in fluid on the opposite side of the membrane.
Breslau et al, in U.S. Pat. No. 4,266,026 disclose use of an anisotropic membrane, but they do not immobilize immunoactive materials within the membrane structure, an essential aspect of the present invention. Moreover, Breslau is not believed to teach a diffusion-only process but one wherein hydraulic pressure is used as a driving force to move mass across his membrane.
A need for an improved blood detoxification system has continued to exist. The present inventors have worked to provide such a system.